GB2194243A

GB2194243A - Improved process for reconsolidated wood production

Info

Publication number: GB2194243A
Application number: GB08724124A
Authority: GB
Inventors: John Douglas Coleman
Original assignee: Commonwealth Scientific and Industrial Research Organization CSIRO
Current assignee: Commonwealth Scientific and Industrial Research Organization CSIRO
Priority date: 1983-11-23
Filing date: 1987-10-14
Publication date: 1988-03-02
Also published as: EP0355858A2; SE8602324L; JP2509063B2; SE8602324D0; SE458347B; NZ210302A; SE8802083D0; DE3482658D1; DE3486310D1; EP0196299B1; EP0196299A4; GB8724124D0; EP0196299A1; EP0355858B1; SE8802083L; EP0355858A3; GB2194243B; DE3486310T2; US4711689A; JPS61500481A

Description

GB2194243A 1 SPECIFICATION example only with reference to the accom

panying drawings in which:

Improved process for reconsolidated wood Figure I is a diagram showing steps in the production process as described in Patent Specification

70 510,845 for forming a reconsolidated wood Australian Patent Specification 510,845 de- product; scribes a reconsolidated wood product formed Figure 2 illustrates a method of adhesive from at least one flexible open lattice work application involving prior wax coating; web of naturally interconnected wood strands Figure 3 is a diagram showing a variation of generally aligned along a common grain direc- 75 the process shown in Fig. 2; and tion, a substantial proportion of said strands Figure 4 is a diagram illustrating a preferred being substantially discrete but incompletely method of effecting compression of webs to separated from each other; said web having form a reconsolidated wood product in accor been consolidated by compression whilst sub- dance with this invention.

stantially maintaining the wood strands aligned 80 Referring firstly to Fig. 1, in the process of along said common grain direction and said Australian Patent Specification 510,845 natural strands being bonded together to hold them in wood logs 10 are first partially broken down, juxapositions assumed pursuant to said con- being passed successively between rollers 12 solidation. of one or more roller pairs to induce cracking That patent specification also describes a 85 and thence progressively open up the log process for forming a reconsolidated wood structure to form it into a web of loosely in product from a flexible open lattice work web terconnected splinter-like strands (called of naturally interconnected wood strands, said 11 splinters" in Patent Specification 510,845).

web being formed by partially rending natural The resultant web, shown at 14 in Fig. 1, is wood so that said said strands are generally 90 of flexible open lattice work form, individual aligned along a common grain direction, a strands maintaining the original grain. direction substantial proportion of said strands being of the wood. Adhesive is then applied to the substantially discrete but incompletely sepa- webs 14 such as by immersion in a suitable rated from each other, said process comprisliquid adhesive in a bath 16 as shown. After ing compressing the web to consolidate the 95 removal of excess adhesive (by means not strands whilst maintaining them such as to shown), a plurality of webs 14 are assembled substantially extend in said original grain direc- together such that the individual webs in the tion and bonding said strands together to hold assemblage are aligned in a common grain di them in juxtapositions assumed pursuant to rection in a suitable mould 18. The assem said consolidation. 100 blage of thus aligned webs is then consoli- In one aspect the invention seeks to provide dated in mould 18 such as by compression an improved process as above described and between the base of the mould and an upper which permits a more economical use of press element 20 as shown, and the adhesive bonding agent as used to bond the web is cured, to form the final product 22.

strands together. 105 Product 22 is characterized in that it com- In accordance with this aspect of the inven- prises a plurality of wood strands which re- tion there is provided a process as described main naturally interconnected and which ex above wherein said bonding is effected by use tend generally in the original grain direction of of a bonding agent and, prior to application of the wood. The strands are bond together by the bonding agent, the said web is subjected 110 the adhesive but are positioned in somewhat to a treatment in which its surface is coated displaced relative locations as compared with with wax. Suitable waxes may be selected the positions occupied in the original log 10.

from the group comprising paraffin waxes but The product 22 has been found to be particu other waxes may be used. larly satisfactory as it possesses good me- In another aspect the invention seeks to im- 115 chanical properties, due to the relatively small prove the dimensional stability of the final pro- degradation of the original wood structure duct produced by the process of specification which is caused by the process, as well as

510,845. good nailability and a generally pleasing In this aspect, the invention contemplates appearance.

effecting the compression step as in the pro- 120 Referring now to Fig. 2, there is shown dia- cess of Specification 510,845, by a first grammatically an additional process step in ac pressing causing application of compressive cordance with this invention and which is not force in one direction transverse to the direc- shown in the process as just described in Fig.

tion of extent of the grain of the web, at least 1. That is to say, before the application of partially releasing said compressive force, foladhesive in the bath 16, the surfaces of the lowed by a further pressing to effect com- webs 14 are coated in a bath 100 containing pression either in said one direction or in a a liquid wax as shown at step 102 in Fig. 2.

direction transverse thereto and also tranverse A suitable liquid wax may be an emulsion of to said direction of extent of the grain. paraffin wax in water but other types of liquid The invention is further described by way of 130 wax may be used.

2 GB2194243A 2 After coating in the bath 100 the webs are sion of the material again occurs. Thus, in this removed therefrom, drained then dried as indi- first pressing, the dimension of the webs may cated at steps 103 and 104 in Fig. 2, and be reduced to the dimension D1 shown. Then, then passed to the aforementioned adhesive in a second step, re-expansion to a dimension bath 16 as shown at step 105 in Fig. 2. 70 D2 is permitted by release of pressure P1 to Following adhesive application, the webs are a lesser pressure P2. Where a hydraulic press removed, drained as shown at step 106 and is used for providing the pressure P1, the then placed, for example, in the mould 18 pressure P2 may be provided simply by re (step 107). The webs are then subjected to leasing the hydraulic pressure so that only the pressure as previously described, whereafter, 75 weight of the compressing structure bears with the pressure maintained, the adhesive is against the webs 14. After the second step, permitted to cure. These latter steps are the webs 14 may be removed and placed in a represented at 108 in Fig. 2. Thereafter, the second press 120 which is arranged to permit formed final product 22 is removed. application of a pressure P3 in a direction With the above described process steps, 80 which is transverse to the initial direction of wax coating as effected in bath 100 minimizes application of pressure in press 118. This the amount of subsequent adhesive pick up so pressure P3 may be arranged to be such as cutting down the required amount of adhesive. to complete the final product an bring it to In that regard, in the absence of wax coating, the desired end density and thickness D3.

a more substantial impregnation with adhesive 85 Curing of the adhesive bonding the webs 14 may occur which is on the one hand unneces- together may be allowed to be completed in sary for the structural purposes of the inven- the press 120 whilst the pressure P3 is main tion and which, on the other hand, is wasteful tained.

of adhesive. Control of adhesive pick up is Although the above process is described as thus achieved by appropriately selecting the 90 using two presses 118, 120 (for simplicity), it wax and the time for which the webs 14 re- will be appreciated that it is possible to devise main in bath 100. presses in which this processing is effected A further benefit from coating the webs 14 without the need to remove the webs from with wax is that the presence of wax thereon one press and insert them into another for increases the resistance of the final product 95 completion of the process. In the described 22 to the ingress of water and thus in use process, too, the pressing is shown, as is enhances the durability of the resultant pro- preferred, as being effected first in a direction duct. parallel to the intended longer cross sectional Fig. 3 shows a variation of the process of dimension of the final product and thence nor- Fig. 2 as applied in the case where the adhe- 100 mal to that cross sectional dimension. How sive is a two-part composition. The adhesive ever, it is possible to reverse the order of may comprise a first component in the form pressing steps.

of a solution of tannin powder in water and a The described arrangement has been ad- second component in the form of a suitable vanced merely by way of explanation and activator such as hexamine dissolved in water. 105 many modifications may be made thereto In such a process, the tannin solution may be without departing from the spirit and scope of mixed with the wax to form the bath 109 the invention as defined in the appended shown in Fig. 3 into which, at the step 110 claims.

shown, the webs 14 are immersed then re

Claims

moved therefrom. The webs are then drained 110 CLAIMS (step 111) prior to

subsequent drying (step 1. A process for forming a reconsolidated 112), and passed to a bath 114 of the afore- wood product from a flexible open lattice mentioned activator (step 113). After immer- work web of naturally interconnected wood sion in the activator for a predetermined time, strands, said web being formed by partially the webs are removed, drained (step 115) and 115 rendering natural wood so that said strands then passed to the mould 18 for consolidation are generally aligned along a common grain and curing as indicated at the steps 116, 117 direction, a substantial proportion of said which are performed in the same fashion as strands being substantially discrete but incom aforedescribed in relation to Fig.
2. pletely separated from each other, said pro- Fig. 4 illustrates a preferred method in ac- 120 cess comprising compressing the web to concordance with this invention for effecting the solidate the strands whilst maintaining them consolidation step in Fig. 1. In this case, the such as to substantially extend in said orginal webs 14 are first laid in a first press 118, grain direction and bonding said strands to (the webs being viewed end-on in Fig. 4). The gether to hold them in juxtapositions assumed webs 14 are then pressed from opposed 125 pursuant to said consolidation, wherein said sides in the press 118 by application of a bonding is effected by use of a bonding agent pressure P1 which may be sufficient to, for and, prior to application of the bonding agent, example, compress the webs to about 50 per- the said web is subjected to a treatment in cent of the desired final density. Thereafter, which its surface is coated with wax.

the pressure is released so that some expan- 130 2. A process as claimed in claim 1
3 GB2194243A 3 wherein said wax is selected from the group direction.

comprising paraffin waxes. 10. A process as claimed in claim 11 3. A process for forming a reconsolidated wherein said first pressing and said further wood product from a flexible open lattice pressing are effected in directions which are work web of naturally interconnected wood 70 normal to each other.

strands, said web being formed by partially rending natural wood so that said strands are Published 1988 at The Patent Office, State House, 66/71 High Holborn, London WC 1 R 4TP. Further copies may be obtained from generally aligned along a common grain direc- The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BF15 3RD.

tion, a substantial proportion of said strands Printed by Burgess & Son (Abingdon) Ltd. Con. 1/87.

being substantially discrete but incompletely separated from each other, said process com prising compressing the web to consolidate the strands whilst maintaining them such as to substantially extend in said original grain direc tion and bonding said strands together to hold them in juxtapositions assumed pursuant to said consolidation, wherein said compressing is effected by a first pressing causing applica tion of compressive force in one direction transverse to the direction of extent of the grain of the web, at least partially relating said compressive force, followed by a further pressing to effect compression either in said one direction or in a direction transverse thereto and also transverse to said direction of extent of the grain.
4. A process as claimed in claim 3 wherein said further pressing is effected in a direction transverse to said one direction.
5. A process as claimed -in claim 4 wherein said first pressing and said further pressing are effected in directions which are normal to each other.
6. A process as claimed in claim 3 wherein said further pressing is effected in said one direction.
7. A process as claimed in any one of claims 3 to 6, wherein said bonding is ef fected by use of a bonding agent and, prior to application of the bonding agent, the said web is subjected to a treatment in which its sur face is coated with wax.
8. A process as claimed in claim 7 wherein said wax is selected from a group comprising paraffin waxes.
9. A process for forming a reconsolidated wood product from a flexible open lattice work web of naturally interconnected wood strands, said web being formed by partially rending natural wood so that said strands are generally aligned along a common grain direc tion, a substantial proportion of said strands being substantially discrete but incompletely separated from each other, said process com prising compressing the web to consolidate the strands whilst maintaining them such as to substantially extend in said original grain direc tion and bonding said strands together to hold them in juxtapositions assumed pursuant to said consolidation, wherein said compressing is effected by first applying pressure in one direction transverse to the direction of extent of the grain and then applying pressure in another direction different to said one direc- tion but also generally transverse to said grain i